1. Field of the Invention
This invention relates generally to compressors for gas turbine engines and more particularly to vibration damping in high pressure ratio centrifugal compressors of the type comprising an inducer section and an impeller section indexed relative thereto.
2. Description of the Prior Art
Gas turbine engines, and particularly engines for vehicular applications, place tremendous demands upon the compressor rotor. For example, rotational speeds of 60,000 to 70,000 rpm or more may be required in conjunction with single stage pressure ratios of up to 6:1 or more over a substantial range of rotational velocities. One arrangement which has been developed to meet these heavy demands is the two part centrifugal compressor comprising an inducer and an impeller. The velocity of the gas (typically air) relative to the blade is highest and often supersonic at the inducer inlet and the blades of the inducer section therefore have more of a disturbing effect on air flow than do the impeller blades. Inducer blades are thus made as thin as practical to minimize this disturbance. However, because of the levels of stress and vibrations to which the inducer blades are subjected during operation, there are practical limits on how thin these blades can be made. If they are made too thin, blade vibrations occur with sufficient amplitude to cause metal fatique and the blades fail under the stress of high velocity rotation.